Tubular electric discharge lamp with integral protective-insulating sleeve

ABSTRACT

A rigid open-ended sleeve of plastic or other light-transmitting material is suspended in telescoped spaced-apart relationship with the glass envelope of an electric lamp by slipping the sleeve over a pair of spaced rubber grommets that compressively grip the envelope. The grommets effect a force fit with the sleeve and the latter is retained in place on the lamp solely by the grommets. In the case of a fluorescent lamp or other type of low-pressure electric discharge lamp, the sleeve serves both as a protective shield against accidental breakage of the envelope and as an insulating jacket which permits the lamp to operate efficiently at low ambient temperatures (-18*C for example). The sleeve can be fabricated from colored plastic or glass to provide a low-cost fluorescent lighting unit that emits light of a selected color and is thus especially adapted for use in outdoor decorative lighting applications.

United States Patent Gilmore et al.

[ 1March I3, 1973 TUBULAR ELECTRIC DISCHARGE LAMP WITII INTEGRALPROTECTIVE- INSULATING SLEEVE Assignee:

Filed:

Inventors: John F. Gilmore, Verona; Roy W.

Epting, Parsippany, both of NJ.

Westinghouse Electric Corporation,

Pittsburgh, Pa.

May 5, 1970 Appl. No.: 34,806

U.S. Cl ..240/ll.4 I-I, 313/25 Int. Cl. ..F2lv 15/00 Field ofSearch..240/5l.l1, l1.4,1.l,3.1,

References Cited UNITED STATES PATENTS Oharenko ..240/1 1.4

Kushner ..240/1.1

Kunins ..240/3.l Hoskins ..240/l1.4 Shanks ..3l3/25 Weiss ..240/l1.4Keiffer ..240/11.4 H

Primary Examiner-James J. Gill Assistant Examiner-Marvin SmollarAttorney-A. T. Stratton, W. D. Palmer and D. S. Buleza [57] ABSTRACTinsulating jacket which permits the lamp to operate efficiently at lowambient temperatures (-18C for example). The sleeve can be fabricatedfrom colored plastic or glass to provide a low-cost fluorescent lightingunit that emits light of a selected colorand is thus especially adaptedfor use in outdoor decorative lighting applications.

4 Claims, 2 Drawing Figures PATENTEUHARISISH 3 720, 25

J0 F. Gilmore and Roy W. Epting BY J fifiu f, 0 AGENT TUBULAR ELECTRICDISCHARGE LAMP WITH INTEGRAL PROTECTIVE-INSULATING SLEEVE CROSSREFERENCE TO RELATED APPLICATION An electric discharge lamp having atubular glass envelope that is protectively enclosed in a tight-fittingsleeve of shrunk oriented plastic, or in a rigid loosefitting sleevethat is held in place by shrunk plastic sleeves, is disclosed inapplication Ser. No. 586,115 of George S. Evans, filed Oct. 12, 1966.

BACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to electric lamps and has particular reference to an improvedfluorescent lamp assembly that is adapted for use in lightingapplications where protection against accidental lamp breakage isdesired and/or low ambient temperatures prevail.

2. Description of the Prior Art Fluorescent lighting units havingintegral protective and thermal-insulating shields or jackets are wellknown in the art. Heretofore, the jacket was held in spaced-apartenclosing relationship with the lamp envelope by a pair of resilientcaps or gaskets that were slipped over the based end portions of thelamp and engaged the adjacent ends of the sleeve thereby providing asealed air space around the entire lamp envelope. A fluorescent lightingunit constructed in this manner is disclosed in US. Pat. No. 3,124,307issued Mar. 10, 1964 to T. E. Hoskins et al. In a more recent design, aportion of the inner surface of a protective glass jacket is coated withreflective material and the ends of the jacket are inserted into annularrecesses in sealing rings of resilient material that are force-fittedover the ends of the lamp. A jacketed fluorescent lamp assembly of suchconstruction is disclosed in US. Pat. No. 3,179,792 issued Apr. 20, 1965to H. Weiss.

While such jacket assemblies achieved the desired objectives ofprotecting the lamp envelopes against accidental breakage and thermallyinsulating the lamps, they were difficult to manufacture on amass-production basis and were quite expensive since they requiredprecision-molded sealing caps or gaskets. Moreover, it has been foundthat when a plastic jacket was used the jacket expands and contracts toa greater degree than the glass envelope with temperature changes, thuscausing the sleeve and gaskets to gradually separate. Under certainlow-temperature conditions, it has also been found that ice sometimesforms under the rubber gaskets which eventually forces them off of theends of the lamp.

SUMMARY OF THE INVENTION The aforementioned problems and disadvantagesencountered with the prior art designs and structures are averted inaccordance with the present invention by mounting a tubular open-endedsleeve on the lamp with a pair of narrow grommets of resilient materialthat compressively grip the lamp envelope and are located inwardly fromthe ends of the sleeve and the base members that are attached to theends of the lamp envelope. The wall thickness of the grommets is socorrelated with the inside diameter of the sleeve that the latter makesa tight frictional fit with the grommets and is securely held in placeon the lamp. The open ends of the sleeve are not restricted orconstrained in any manner and the sleeve is thus, suspended intelescoped and shielding relationship with the lamp envelope. The sleeveis accordingly free to expand and contract relative to the envelopewithout slipping off of the lamp and can thus be made of plastic, eventhough the lamp is intended for use in low-temperature environments. Theresulting lamp assembly is light in weight, easy to assemble andrequires inexpensive sleeve and sleeveretaining components.

BRIEF DESCRIPTION OF THE DRAWING A better understanding of the inventionwill be obtained by referring to the exemplary embodiment shown in theaccompanying drawing, wherein:

FIG. 1 is a side elevational view, partly in section, of a fluorescentlighting unit incorporating the invention; and

FIG. 2 is an end view of the lighting unit.

DESCRIPTION OF THE PREFERRED EMBODIMENT The improved lighting unit 10,as illustrated in FIGS. 1 and 2, consists of an elongated fluorescentlamp L that has a cylindrical glass envelope 12 which is protectivelydisposed within an open-ended tubular sleeve 14 of rigidlight-transmitting material. The sleeve 14 is suspended in spaced-aparttelescoped relationship with the envelope 12 by a pair of resilientbrand-like members such as narrow rubber grommets 15 and 16 that arecompressively sandwiched between the sleeve and the ends of the lampenvelope, as shown. As will be noted, the sleeve 14 is shorter than theoverall length of the lamp L but is of substantially the same length asthe lamp envelope l2 and is also cylindrical but slightly larger indiameter so that an annular air space S is provided which surrounds andextends along almost the entire length of the envelope. The sleeve 14can be fabricated from any suitable light-transmitting material, such asglass, but is preferably made of plastic in order to reduce the weightand cost of the lighting unit 10.

In the case of a conventional 40 watt T12 fluorescent lamp L that has anouter diameter of about 38 mm. and a nominal overall length ofapproximately 122 centimeters, the rubber grommets 15 and 16 have aninside diameter of about 38 mm. and are spaced a predetermined distanceX inwardly from the respective open ends of the sleeve 14 and from thebase members 17 that are attached to the sealed ends of the envelope 12.For a lamp of the size described, this spacing is approximately 6 mm.and allows the sleeve 14 to move relative to the lamp L (as the ambienttemperature changes) without becoming disengaged from the envelope 12.

The fluorescent lamp L is of conventional construction and contains anionizable medium consisting of a suitable starting gas, such as neon ora mixture of neon and argon at low pressure, and a predetermined amountof mercury. A pair of spaced electrodes (not shown) are sealed into theenvelope 12 and are electrically connected to pin terminals 18 anchoredin each of the respective base members 17. The energized electrodes, inconjunction with the mercury and gas fill, initiate and sustain anelectric discharge within the lamp L which excites a layer of phosphor(not shown) coated on the inner surfaces of the envelope 12 in the wellknown manner.

In the case of an envelope which has an outer diameter of about 38 mm.as mentioned above, excellent results have been obtained by using aclear transparent sleeve of extruded polycarbonate resin having a wallthickness of approximately 1 mm. and an inside diameter of about 39.6mm. The rubber grommets were 3 mm. wide and had a uniform wall thicknessof 1/16 inch (about 1.6 mm.). The air space between the sleeve andenvelope was, accordingly, 1.6 mm. and this permitted the lamp tooperate at ambient temperatures in the order of -l8C with practically noloss in light output.

Polycarbonate resin sleeves are available in a variety of tubular sizes,wall thicknesses and colors (red, pink, gold, blue, green, etc.).

With lamps longer than 122 centimeters (for example, 183 cm. or 244cm.), three grommets are preferably used and are spaced apart distancesequal to about one-third of the lamp length. If a plastic sleeve isused, the inward-spacing dimension X will also be increased toaccommodate the larger increments of Iongitudinal expansion andcontraction which will occur under varying ambient temperatures due tothe longer length of the sleeve.

It will be apparent from the foregoing that the invention provides aninexpensive lighting unit that is light in weight and can be easily andefficiently assembled by simply placing the grommets on the finishedlamp and forcibly slipping the sleeve over the grommets. In the case offluorescent lamps or other electric discharge lamps, the inventionpermits the units to be safely used in applications where accidentalbulb breakage would be hazardous and also provides efficient coloredlight sources that can be used in outdoor decorative lightingapplications, such as amusement parks and the like.

We claim as our invention:

1. A lighting unit comprising, in combination;

an electric lamp having a tubular glass envelope,

a protective shield for said envelope consisting of a rigid tubularopen-ended sleeve of light-transmitting plastic that (a) is larger thanand is suspended in spaced-apart telescoped relationship with saidenvelope, (b) is shorter than said lamp, and (c) expands and contractsto a greater degree than said glass envelope under varying ambienttemperature conditions, and

means retaining said plastic sleeve on the lamp in the aforesaidrelationship with said envelope comprising a plurality of narrowband-like members of resilient material that encircle the envelope atspaced points along its length and are located between said envelope andsleeve, said retaining members being of such size that theycompressively grip the encircled parts of the envelope and are in tightfrictional engagement with the overlying encircling portions of saidsleeve so that the sleeve is securely anchored in place on the lampsolely by said retaining members,

the retaining members that are located at the ends of said lamp beingdisposed inwardly a predetermined distance from the respective ends ofboth the sieeve and envelope such that the plastic sleeve is free andable to expand and contract relative to the glass envelope un er varyingambient temperature conditions without forcing the outermost retainingmembers off of said lamp.

2. The combination of claim 1 wherein;

said electric lamp comprises a fluorescent lamp that contains anionizable medium and a pair of spaced electrodes which are connected toterminals that are located at and protrude beyond the respective ends ofthe lamp envelope and are anchored in base members fastened to the endsof said envelope,

said open-ended plastic sleeve is of substantially the same length asthe envelope and is so positioned that said base members and terminalsare exposed,

said retaining members comprise rubber grommets that are spaced inwardlyfrom the respective base members, and

the distance the outermost grommets are spaced inwardly from therespective ends of the sleeve and base members is correlated with thelength of the lamp and increases as the lamp length increases.

3. The combination of claim 2 wherein;

said open-ended sleeve is composed of polycarbonate resin, and

said rubber grommets are of substantially uniform wall thickness.

4. The combination of claim 2 wherein;

said fluorescent lamp has a nominal length of approximately 122centimeters, and

the grommets located at the ends of said lamp are disposed approximately6 mm. inwardly from the respective ends of the sleeve and base members.

1. A lighting unit comprising, in combination; an electric lamp having atubular glass envelope, a protective shield for said envelope consistingof a rigid tubular open-ended sleeve of light-transmitting plastic that(a) is larger than and is suspended in spaced-apart telescopedrelationship with said envelope, (b) is shorter than said lamp, and (c)expands and contracts to a greater degree than said glass envelope undervarying ambient temperature conditions, and means retaining said plasticsleeve on the lamp in the aforesaid relationship with said envelopecomprising a plurality of narrow band-like members of resilient materialthat encircle the envelope at spaced points along its length and arelocated between said envelope and sleeve, said retaining members beingof such size that they compressively grip the encircled parts of theenvelope and are in tight frictional engagement with the overlyingencircling portions of said sleeve so that the sleeve is securelyanchored in place on the lamp solely by said retaining members, theretaining members that are located at the ends of said lamp beingdisposed inwardly a predetermined distance from the respective ends ofboth the sleeve and envelope such that the plastic sleeve is free andable to expand and contract relative to the glass envelope under varyingambient temperature conditions without forcing the outermost retainingmembers off of said lamp.
 1. A lighting unit comprising, in combination;an electric lamp having a tubular glass envelope, a protective shieldfor said envelope consisting of a rigid tubular open-ended sleeve oflight-transmitting plastic that (a) is larger than and is suspended inspaced-apart telescoped relationship with said envelope, (b) is shorterthan said lamp, and (c) expands and contracts to a greater degree thansaid glass envelope under varying ambient temperature conditions, andmeans retaining said plastic sleeve on the lamp in the aforesaidrelationship with said envelope comprising a plurality of narrowband-like members of resilient material that encircle the envelope atspaced points along its length and are located between said envelope andsleeve, said retaining members being of such size that theycompressively grip the encircled parts of the envelope and are in tightfrictional engagement with the overlying encircling portions of saidsleeve so that the sleeve is securely anchored in place on the lampsolely by said retaining members, the retaining members that are locatedat the ends of said lamp being disposed inwardly a predetermineddistance from the respective ends of both the sleeve and envelope suchthat the plastic sleeve is free and able to expand and contract relativeto the glass envelope under varying ambient temperature conditionswithout forcing the outermost retaining members off of said lamp.
 2. Thecombination of claim 1 wherein; said electric lamp comprises afluorescent lamp that contains an ionizable medium and a pair of spacedelectrodes which are connected to terminals that are located at andprotrude beyond the respective ends of the lamp envelope and areanchored in base members fastened to the ends of said envelope, saidopen-ended plastic sleeve is of substantially the same length as theenvelope and is so positioned that said base members and terminals areexposed, said retaining members comprise rubber grommets that are spAcedinwardly from the respective base members, and the distance theoutermost grommets are spaced inwardly from the respective ends of thesleeve and base members is correlated with the length of the lamp andincreases as the lamp length increases.
 3. The combination of claim 2wherein; said open-ended sleeve is composed of polycarbonate resin, andsaid rubber grommets are of substantially uniform wall thickness.